Factors controlling Mn and Zn contents in leaves of silver and downy birch in acidified soils of Central Europe and Norway.

In Central European mountain forests, foliar element concentrations (FECs) of manganese (Mn) in silver birch (Betula pendula Roth) are occasionally approximately 5000 mg kg-1 and can represent stress for these plants. Factors controlling the Mn FECs in silver birch in Central Europe and downy birch (Betula pubescens Ehrh.) in Norway have not yet been fully deciphered. In this study, the Central European silver birch specimens were sampled in 2022. The samples were analysed by X-ray fluorescence spectroscopy. Norwegian data were obtained from the literature. Mn FECs are commonly negatively correlated with magnesium and, in certain areas, with potassium. Mn FECs are simultaneously elevated with zinc (Zn), likely because of soil acidification and anthropogenic emissions. Mn FECs in birch were previously thought to be related to altitude, which was assigned to (i) downslope washes of Mn or (ii) the historical load of acid emissions. The highest Mn FECs in silver birch were found in the Harz Mountains, Germany, and have been attributed to historical atmospheric contamination and the abundance of soils on felsic silicic rocks poorly buffering acid rains. The historical emission load from iron and steel production was hypothesised to be the cause of elevated Mn and Zn FECs in the Beskid Mountains, Czech Republic. Mn FECs in birch can be used to map historical soil acidification caused by industrial emissions. Zn FECs in birches can reflect soil contamination by this element.

Mobilisation of Cd, Mn, and Zn in floodplains by action of plants and its consequences for spreading historical contamination and fluvial geochemistry.

Cadmium, Mn, and Zn are mobilised by plants commonly growing in floodplains, most notably willows (Salix) and alder (Alnus). These plants accumulate unwanted elements (Cd) or excessive element concentrations (Mn, Zn) in their foliage, thus introducing them into the food web and enriching them in floodplain surface by litterfall. In floodplain of the Litavka River in Czechia, contaminated by historical mining activities, up to 100 mg kg-1 Cd and up to several thousand mg kg-1 Mn and Zn are present in willow leaves in autumn, probably close maxima for sustainable plant growth. Willows and alders show seasonal growth of their foliar Mn and Zn. The willow leaves showed Cd/Zn larger than contaminated fluvisol of the Litavka River. Senesced willow leaves thus contribute to spread of risk elements from historically contaminated floodplains back to river water even without the bank erosion. Alders and willows alter geochemical cycles of Cd, Mn, and Zn in fluvial systems and increase Cd/Zn and Mn/Fe concentration ratios and Cd and Mn concentrations in fluvially transported particles relative to global geochemical averages as well as relative to floodplain sediments. Willows, in particular Salix fragilis L., S. aurita L, and S. cinerea L are particularly important "plant pumps". Other common floodplain plants, such as bird cherry (Prunus padus L.) and herbaceous plants (common nettle, Urtica dioica L. and grasses, Poaceae) do not contribute to those phenomena.

Reconstructing atmospheric Hg levels near the oldest chemical factory in central Europe using a tree ring archive.

The Chemical Factory in Marktredwitz (CFM) is known as the oldest chemical factory in Germany (1778-1985), and from the beginning of the 20th century focused primarily on the production of mercury (Hg) compounds. Due to extensive pollution, together with employee health issues, the CFM was shut in 1985 by a government order and remediation works proceeded from 1986 to 1993. In this study, tree ring archives of European Larch (Larix decidua Mill.) were used to reconstruct changes of air Hg levels near the CFM. Mercury concentrations in larch boles decreased from 80.6 µg kg-1 at a distance of 0.34 km-3.4 µg kg-1 at a distance of 16 km. The temporal trend of atmospheric Hg emissions from the CFM reconstructed from the tree ring archives showed two main peaks. The first was in the 1920s, with a maximum tree ring Hg concentration 249.1 ± 43.9 µg kg-1 coinciding with when the factory had a worldwide monopoly on the production of Hg-based seed dressing fungicide. The second peak in the 1970s, with a maximum tree ring Hg concentration of 116.4 ± 6.3 µg kg-1, was associated with a peak in the general usage and production of Hg chemicals and goods. We used the tree ring record to reconstruct past atmospheric Hg levels using a simple model of Hg distribution between the larch tree rings and atmosphere. The precision of the tree ring model was checked against the results of air Hg measurements during the CFM remediation 30 years ago. According to the tree ring archives, the highest air Hg concentrations in the 1920s in Marktredwitz were over 70 ng m-3. Current air Hg levels of 1.18 ng m-3, assessed in the city of Marktredwitz, indicate the lowest air Hg in the past 150 years, underscoring the effective remediation of the CFM premises 30 years ago.

Uptake of Cd, Pb, U, and Zn by plants in floodplain pollution hotspots contributes to secondary contamination.

Willows, woody plants of genus Salix common in floodplains of temperate regions, act as plant pumps and translocate the Cd and Zn in the soil profiles of uncontaminated and weakly contaminated floodplains from the sediment bulk to the top strata. We suggest this process occurs because the Cd and Zn concentrations in willow leaves exceed those in the sediments. Senescing foliage of plant species common in floodplains can increase the Cd and Zn ratios as compared to other elements (Pb and common 'lithogenic elements' such as Al) in the top strata of all floodplains, including those that have been severely contaminated. The top enrichment is caused by the root uptake of specific elements by growing plants, which is followed by foliage deposition. Neither the shallow groundwater nor the plant foliage shows that Cd, Zn, and Pb concentrations are related to those in the sediments, but they clearly reflect the shallow groundwater pH, with the risk element mobilised by the acidity that is typical for the subsurface sediments in floodplains. The effect that plants have on the Pb in floodplains is significantly lower than that observed for Cd and Zn, while U can be considered even less mobile than Pb. Groundwater and plant leaves can contribute to secondary contamination with Cd and Zn from floodplain pollution hotspots, meaning that plants can accumulate these elements on the floodplain surface or even return them back to the fluvial transport, even if bank erosion would not occur. For Pb and U at the sites studied, these risks were negligible.

A Review of Flood-Related Storage and Remobilization of Heavy Metal Pollutants in River Systems.

Recently observed rapid climate changes have focused the attention of researchers and river managers on the possible effects of increased flooding frequency on the mobilization and redistribution of historical pollutants within some river systems. This text summarizes regularities in the flood-related transport, channel-to-floodplain transfer, and storage and remobilization of heavy metals, which are the most persistent environmental pollutants in river systems. Metal-dispersal processes are essentially much more variable in alluvia than in soils of non-inundated areas due to the effects of flood-sediment sorting and the mixing of pollutants with grains of different origins in a catchment, resulting in changes of one to two orders of magnitude in metal content over distances of centimetres. Furthermore, metal remobilization can be more intensive in alluvia than in soils as a result of bank erosion, prolonged floodplain inundation associated with reducing conditions alternating with oxygen-driven processes of dry periods and frequent water-table fluctuations, which affect the distribution of metals at low-lying strata. Moreover, metal storage and remobilization are controlled by river channelization, but their influence depends on the period and extent of the engineering works. Generally, artificial structures such as groynes, dams or cut-off channels performed before pollution periods favour the entrapment of polluted sediments, whereas the floodplains of lined river channels that adjust to new, post-channelization hydraulic conditions become a permanent sink for fine polluted sediments, which accumulate solely during overbank flows. Metal mobilization in such floodplains takes place only by slow leaching, and their sediments, which accrete at a moderate rate, are the best archives of the catchment pollution with heavy metals.

TiO2-graphene oxide nanocomposite as advanced photocatalytic materials.

BACKGROUND: Graphene oxide composites with photocatalysts may exhibit better properties than pure photocatalysts via improvement of their textural and electronic properties. RESULTS: TiO2-Graphene Oxide (TiO2 - GO) nanocomposite was prepared by thermal hydrolysis of suspension with graphene oxide (GO) nanosheets and titania peroxo-complex. The characterization of graphene oxide nanosheets was provided by using an atomic force microscope and Raman spectroscopy. The prepared nanocomposites samples were characterized by Brunauer-Emmett-Teller surface area and Barrett-Joiner-Halenda porosity, X-ray Diffraction, Infrared Spectroscopy, Raman Spectroscopy and Transmission Electron Microscopy. UV/VIS diffuse reflectance spectroscopy was employed to estimate band-gap energies. From the TiO2 - GO samples, a 300 µm thin layer on a piece of glass 10×15 cm was created. The photocatalytic activity of the prepared layers was assessed from the kinetics of the photocatalytic degradation of butane in the gas phase. CONCLUSIONS: The best photocatalytic activity under UV was observed for sample denoted TiGO_100 (k = 0.03012 h-1), while sample labeled TiGO_075 (k = 0.00774 h-1) demonstrated the best activity under visible light.

Hydrogen peroxide route to Sn-doped titania photocatalysts.

BACKGROUND: The work aims at improving photocatalytic activity of titania under Vis light irradiation using modification by Sn ions and an original, simple synthesis method. Tin-doped titania catalysts were prepared by thermal hydrolysis of aqueous solutions of titanium peroxo-complexes in the presence of SnCl4 or SnCl2 using an original, proprietary "one pot" synthesis not employing organic solvents, metallo-organic precursors, autoclave aging nor post-synthesis calcination. The products were characterized in details by powder diffraction, XPS, UV-vis, IR, and Raman spectroscopies, electron microscopy and surface area and porosity measurements RESULTS: The presence of tin in synthesis mixtures favors the formation of rutile and brookite at the expense of anatase, decreases the particle size of all formed titania polymorphs, and extends light absorption of titania to visible light region >400 nm by both red shift of the absorption edge and introduction of new chromophores. The photocatalytic activity of titania under UV irradiation and >400 nm light was tested by decomposition kinetics of Orange II dye in aqueous solution CONCLUSIONS: Doping by Sn improves titania photoactivity under UV light and affords considerable photoactivity under >400 nm light due to increased specific surface area and a phase heterogeneity of the Sn-doped titania powders.

Experimental in situ transformation of Pb smelter fly ash in acidic soils.

Soils in the vicinity of nonferrous metal smelters are often highly polluted by inorganic contaminants released from particulate emissions. We used a technique with double polyamide experimental bags (1-µm mesh) to study the in situ transformation of fly ash (FA) from a secondary Pb smelter in acidic soil profiles. Between 62 and 66% of the FA dissolved after one year's exposure in the soils, leading to complete dissolution of primary caracolite (Na(3)Pb(2)(SO(4))(3)Cl) and KPb(2)Cl(5), with formation of secondary anglesite (PbSO(4)), minor PbSO(3), and trace carbonates. Release of Pb was pH-dependent, whereas not for Cd and Zn. Significant amounts of metals (mainly Cd and Zn) partitioned into labile soil fractions. The field data agreed with laboratory pH-static leaching tests performed on FA, which was washed before the experiment to remove soluble salts. This indicates that appropriate laboratory leaching can accurately predict FA behavior in real-life scenarios (e.g., exposure in soil).

Ge4+ doped TiO2 for stoichiometric degradation of warfare agents.

Germanium doped TiO(2) was prepared by homogeneous hydrolysis of aqueous solutions of GeCl(4) and TiOSO(4) with urea. The synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, EDS analysis, specific surface area (BET) and porosity determination (BJH). Ge(4+) doping increases surface area and content of amorphous phase in prepared samples. These oxides were used in an experimental evaluation of their reactivity with chemical warfare agent, sulphur mustard, soman and agent VX. Ge(4+) doping worsens sulphur mustard degradation and improves soman and agent VX degradation. The best degree of removal (degradation), 100% of soman, 99% of agent VX and 95% of sulphur mustard, is achieved with sample with 2 wt.% of germanium.

New generation photocatalysts: how tungsten influences the nanostructure and photocatalytic activity of TiO2 in the UV and visible regions.

Tungsten-doped anatase was prepared by a thermal hydrolysis of aqueous solutions of peroxo complexes of titanium and tungsten. The synthesized samples included X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, Raman spectroscopy, specific surface area, and porosity determination. W doping resulted in a decrease of the unit-cell volume of anatase at lower W contents and an increase at higher W contents. The position of the most intense Raman band of the E(g) mode (near 147 cm(-1)) also has a local minimum at medium-doped titania (1.1-3.6% W in titania). W doping increases the temperature of anatase-to-rutile transformation by about 100 °C compared with nondoped anatase. The photocatalytic activity of doped titania samples was determined by decomposition of Orange II dye during irradiation at 365 and 400 nm. Specimens with moderate W doping (1.0-3.3% W) perform best: they enhance the corresponding reaction rates 10 times at 365 nm and 5 times at 400 nm, respectively, compared with pure titania obtained under the same set of synthesis conditions.

Sulphur mustard degradation on zirconium doped Ti-Fe oxides.

Zirconium doped mixed nanodispersive oxides of Ti and Fe were prepared by homogeneous hydrolysis of sulphate salts with urea in aqueous solutions. Synthesized nanodispersive metal oxide hydroxides were characterised as the Brunauer-Emmett-Teller (BET) surface area and Barrett-Joiner-Halenda porosity (BJH), X-ray diffraction (XRD), infrared (IR) spectroscopy, scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) microanalysis, and acid-base titration. These oxides were taken for an experimental evaluation of their reactivity with sulphur mustard (chemical warfare agent HD or bis(2-chloroethyl)sulphide). The presence of Zr(4+) dopant tends to increase both the surface area and the surface hydroxylation of the resulting doped oxides in such a manner that it can contribute to enabling the substrate adsorption at the oxide surface and thus accelerate the rate of degradation of warfare agents. The addition of Zr(4+) to the hydrolysis of ferric sulphate with urea shifts the reaction route and promotes formation of goethite at the expense of ferrihydrite. We discovered that Zr(4+) doped oxo-hydroxides of Ti and Fe exhibit a higher degradation activity towards sulphur mustard than any other yet reported reactive sorbents. The reaction rate constant of the slower parallel reaction of the most efficient reactive sorbents is increased with the increasing amount of surface base sites.

Evolution of bioavailable copper and major soil cations in contaminated soils treated with ethylenediaminedisuccinate: a two-year experiment.

This study evaluates the long-term behavior of metals in soils treated with ethylenediaminedisuccinate for remediation purposes. The addition of the chelant led to a significant increase of water-extractable copper, iron, aluminum contents and their uptake by poplar. Increased concentrations of the metals were present in the soil solution even after the 2 years of the experiment (up to a 30-, 170- and 270-fold increase for copper, iron and aluminum, respectively). Therefore, soils treated with chelants must be monitored not only for the targeted metal concentrations but also for major soil cations originating from chelant-induced dissolution of soil oxides.

Thallium dynamics in contrasting light sandy soils--soil vulnerability assessment to anthropogenic contamination.

The influence of different soil conditions and the presence of LMWOA (Low Molecular Weight Organic Acids) on anthropogenic Tl dynamics were discussed in this study. A shift from the "labile" to the residual fraction during the ageing was identified, indicating Tl incorporation into stable phases (e.g., illite and/or amorphous silicates). The increased water-soluble Tl concentration (1.8-fold, in maximum) after the split application of LMWOA (simulating root exudation) was observed in all soils; partial dissolution of relatively "insoluble" Tl-bearing phases (silicates and eventually oxides) in the presence of LMWOA is suggested. Thermodynamic modeling showed that Tl mobilization in the presence of citric and oxalic acids was indirect and could be attributed to complexation of major elements (Ca, Mg, Al) originating from the dissolution of various soil phases. On the contrary, H(+)-promoted dissolution by acetic acid was assumed as the predominant mechanism of Tl mobilization. Manganese(III,IV) oxides, illite and probably amorphous silicates were evaluated as the dominant phases responsible for Tl retention in the soils. In carbonate-rich soils, Tl coprecipitation with the newly formed carbonates seems to be an important factor influencing Tl release. Therefore, we suggest data on CEC, pH(ZPC) and soil mineralogy to be critical for assessment of Tl behavior in soil systems.

Assessment of the BCR sequential extraction procedure for thallium fractionation using synthetic mineral mixtures.

This work focused on the specific behavior of Tl-bearing phases in the BCR (Community Bureau of Reference) sequential extraction (SE) scheme, namely Tl-bearing ferrihydrite, goethite, birnessite, calcite, illite, sphalerite and feldspar in their simple model mixtures with quartz. Several significant discrepancies between the obtained and expected behaviors of these phases in the BCR SE were observed. The amount of Tl released as the exchangeable/acid-extractable fraction (55-82% of the total Tl content) showed a substantial H(+)-promoted dissolution of all Fe(III) and Mn(III, IV) oxides (corresponding to up to 61% of solid Fe dissolved) and incongruent (increased) extraction of Tl from ferrihydrite and goethite. Reductive conditions of the second SE step were insufficient to complete goethite dissolution with corresponding Tl amount retained in the solid phase. Similarly, insufficient oxidation of sphalerite and lower Tl recovery of the oxidisable fraction was identified. In contrast, the BCR SE seems to produce well predictable results of Tl leaching from Tl-bearing calcite and feldspar. Only 70% of total Tl content was extracted from Tl-modified illite in the exchangeable/acid-extractable step, while 30% was associated with the reducible and residual fractions, i.e., Tl was strongly fixed to the illite matrix.

Cadmium, lead and zinc leaching from smelter fly ash in simple organic acids--simulators of rhizospheric soil solutions.

Emissions from base-metal smelters are responsible for high contamination of the surrounding soils. Fly ash from a secondary Pb smelter was submitted to a batch leaching procedure (0.5-168 h) in 500 microM solutions of acetic, citric, or oxalic acids to simulate the release of toxic metals (Cd, Pb, Zn) in rhizosphere-like environments. Organic acids increased dissolution of fly ash by a factor of 1.3. Cadmium and Pb formed mobile chloro- and sulphate-complexes, whereas Zn partly present in a citrate (Zn-citrate(-)) complex is expected to be less mobile due to sorption onto the positively charged surfaces of hydrous ferric oxides (HFO) and organic matter (OM) in acidic soil.

The pH-dependent leaching of inorganic contaminants from secondary lead smelter fly ash.

The leaching behaviour of fly ash (FA) from a secondary Pb smelter was assessed using the pH-static leaching experiment according to prEN 14997 (pH range 3-11) coupled with mineralogical investigation of the leached FA by XRD and Rietveld analyses and thermodynamic modelling using PHREEQC-2. The procedure was performed on fresh FA and FA washed at a cumulative L/S ratio of 60l/kg to remove readily soluble salts. For both fresh and washed FA, high amounts of inorganic contaminants were released under acidic conditions, exhibiting L-shaped leaching patterns: up to 300g Pb/kg, 4.5g Cd/kg, 4g Zn/kg, 1.05g As/kg and 70mg Sb/kg. The washing of soluble salts significantly decreased the leachability of Cd, Zn, As and Sb and increased the release of Pb, especially under acidic conditions. The leaching of fresh FA removed part of primary caracolite and all the KPb(2)Cl(5) and NaCl. The Pb release was controlled by the precipitation of anglesite and PbSO(3) under acidic conditions and of laurionite and carbonates (hydrocerussite and phosgenite) under alkaline conditions. In contrast, the washed FA was composed mainly of anglesite and PbSO(3), both phases being the main solubility-controlling phases for Pb over the whole studied pH range.

Modified aluminosilicates as low-cost sorbents of As(III) from anoxic groundwater.

The utilization of low-grade clay materials as selective sorbents represents one of the most effective possibilities of As removal from contaminated water reservoirs. The simple pre-treatment of these materials with Fe (Al, Mn) salts can significantly improve their sorption affinity to As oxyanions. The natural kaolin calcined at 550 degrees C (mostly metakaolin) and raw bentonite (mostly montmorillonite) pre-treated with Fe(II), Fe(III), Al(III) and Mn(II) salts were used to remove of As from the model anoxic groundwater with As(III) concentration about 0.5 and 10 mg L(-1). All the pre-treating methods were appropriate for bentonite; the efficiency of As(III) sorption varied from 92 to >99%, by the sorption capacity higher than 4.5 mg g(-1). In the case of metakaolin, Fe(II)- and Mn(II)-treatments proved the high sorption efficiency (>97%), while only <50% of As was removed after Fe(III) and Al(III) pre-treatment. The sorption capacities of treated metakaolin ranged from 0.1 to 2.0 mg g(-1).

Controls on metal leaching from secondary Pb smelter air-pollution-control residues.

Air-pollution-control (APC) residues are among the most toxic waste materials from secondary Pb metallurgy. Two distinct APC residues collected from bag-type filters of one Czech secondary Pb smelter were subjected to leaching experiments to determine the mineralogical and geochemical controls on leaching of metallic contaminants (Cd, Cu, Pb, Zn). A kinetic 720-h leaching test in deionized water at a liquid-to-solid (L/S) ratio of 10 L kg(-1) and a 48-h leaching test at various L/S ratios (0.5, 1, 5, 10, 50, 100, 500, and 1000 L kg(-1)) were performed and coupled with the mineralogical investigation of solid residues (TEM/EDS, XRD) and PHREEQC-2 speciation-solubility modeling. The rapid release of contaminants into the solution at all the L/S ratios showed the rapid dissolution of primary phases. The leaching at high L/S ratios, representing long-term predictions of leaching behavior, showed that primary alkaline sulfates and chlorides (Na3Pb2(S04)3Cl and KCl.2PbCl2) were dissolved and anglesite (PbSO4) was formed as their final and stable alteration product. Primary amorphous PbSO3 partly crystallized during leaching and oxidized to anglesite. These results are consistent with the mineralogical investigation of soils exposed for decades to Pb smelter emissions, where only anglesite was detected. The leaching experiments showed thatwashing residues at L/S >50 accompanied by spontaneous anglesite precipitation can be an alternative for improved technological treatment of these residues. Although this process would require further treatment of contaminated effluent, the newly precipitated anglesite is more favorable than the primary APC residue phases for an efficient metallurgical recovery of Pb.

Assessment of single extractions for the determination of mobile forms of metals in highly polluted soils and sediments--analytical and thermodynamic approaches.

Highly polluted forest/tilled soils and stream sediments from a mining and smelting area were subjected to single-extraction procedures to determine the extractable contents of Cd, Cu, Pb, and Zn. The results obtained from four widely used operationally defined single extraction tests were compared: deionised water, 0.01 mol L(-1) CaCl2, 1 mol L(-1) NH4NO3 and 0.005 mol L(-1) DTPA. The analytical data were coupled with measurement of the pH and Eh in extracts, mineralogical investigations and thermodynamic modelling using the PHREEQC-2 code. The changes in the pH of the equilibrated suspensions significantly influenced the metal extractabilities, with higher values in the lower pH regions. Although the DTPA procedure generally extracted the highest amounts of metals, it was found to be unsuitable for highly organic acidic forest soils, where anionic metal-DTPA complexes are assumed to be re-adsorbed on the positively charged surfaces of soil organic matter and oxides. The NH4NO3 extraction was also unsuitable due to the high ionic strength (1 mol L(-1)), limiting the use of the thermodynamic speciation model and the formation of the Cu(NH3)2+ complex, leading to acidification of the suspension. 0.01 mol L(-1) CaCl2 can be proposed as the most appropriate extraction medium, suitable for speciation modelling and analytical determinations using ICP-techniques and having an ionic strength similar to that of the soil solution. The metals are present in free ionic forms or chlorocomplexes in the CaCl2 extracts, preventing their re-adsorption on the positively charged surfaces of soil solids (organic matter, Fe- and Mn-oxides) in acidic and circum-neutral conditions.

Sorption of As(V) on aluminosilicates treated with Fe(II) nanoparticles.

Adsorption of arsenic on clay surfaces is important for the natural and simulated removal of arsenic species from aqueous environments. In this investigation, three samples of clay minerals (natural metakaoline, natural clinoptilolite-rich tuff, and synthetic zeolite) in both untreated and Fe-treated forms were used for the sorption of arsenate from model aqueous solution. The treatment of minerals consisted of exposing them to concentrated solution of Fe(II). Within this process the mineral surface has been laden with Fe(III) oxi(hydroxides) whose high affinity for the As(V) adsorption is well known. In all investigated systems the sorption capacity of Fe(II)-treated sorbents increased significantly in comparison to the untreated material (from about 0.5 to >20.0 mg/g, which represented more than 95% of the total As removal). The changes of Fe-bearing particles in the course of treating process and subsequent As sorption were investigated by the diffuse reflectance spectroscopy and the voltammetry of microparticles. IR spectra of treated and As(V)-saturated solids showed characteristic bands caused by Fe(III)SO(4), Fe(III)O, and AsO vibrations. In untreated As(V)-saturated solids no significant AsO vibrations were observed due to the negligible content of sorbed arsenate.